Police estimated the crowd at about 1,000, though at times it easily might have been twice that size. No arrests were reported.

Police Superintendent Garry McCarthy was at Federal Plaza and after the rally ended he pronounced the day a success.

"I think it went extremely well,” he said. "We haven't had any issues."

"I think our training is good and frankly it wasn't that big a crowd," McCarthy added.

The police followed normal parade and protest protocols, McCarthy said, and had backups who were not called upon.

He declined to predict what kind of crowds the NATO summit would draw.

There were other rallies around the country marking the May 1 celebration of organized labor and the Occupy movement sought to use many of them to re-energize its organization.

Occupy Cleveland canceled its events "out of respect for the city" after U.S. authorities announced the arrest of five self-described anarchists in the Cleveland area on suspicion of plotting to blow up a four-lane highway bridge over a national park.

Occupy Cleveland said in a statement the men arrested were associated with their movement but that "they were in no way representing or acting on behalf of Occupy Cleveland" and that the group was committed to non-violent protest.

Over the next several months, some of the men discussed coming to Chicago for what at that time was scheduled to be back-to-back meetings of the G-8 and NATO leaders in mid-May, according to the federal criminal complaint. The G-8 meeting of government financial leaders was later rescheduled for Camp David, Md., but the NATO summit of leaders from around the world is set for May 20-21 in Chicago.

According to the complaint, one of the defendants used broad and boastful language to predict anarchists would wreak havoc in Cleveland as a prelude to disrupting Chicago during the summit, saying the goal was to spread rioting and destruction in every major city.

The Chicago FBI office issued a statement that "there was no evidence developed of a planned or credible threat" to the upcoming summit or Chicago.

May Day in Chicago started with small groups of protesters demonstrating against bank bailouts in the downtown financial district. When protesters tried to block the doors to the Bank of America, uniformed police moved them away.

"The cavalry is here!" one protester shouted when police on bikes pulled up.

About 40 protesters chanted about Bank of America getting federal benefits: "The banks got bailed out and we got sold out!"

One man on the corner wore a mock security uniform with a badge that said "we are the 99 percent." He said he was keeping order among the group and told one man to tear up a sign that said "(expletive) the police."

"I like to resolve issues. I will get rid of the problem if there is one. We want a clean protest," said Tony Norris.

Eventually several dozen Occupy demonstrators headed west through the Loop toward a noon rally at Union Park. Traffic stopped at several intersections while the protesters walked through. Bicycle officers lined up to try and prevent protesters from marching in the streets, but many protesters ran ahead and back into the roadway.

Onlookers watched from the windows of office towers or shot photos and videos of the march from the sidewalk.

"Get a job, you jerks!" a man in a suit yelled as the protesters crossed Wacker Drive.

The traditional May Day rally at Union Park on the Near West Side had as many as 1,000 people supporting labor and human rights causes. Union members, anti-war protesters and supporters of the Communist and Socialist parties were all in attendance. Vendors sold cotton candy.

Among the speakers was Andy Thayer, the leader of an anti-war group planning a major NATO demonstration on the first day of the summit, May 20. Also attending were controversial activists Bill Ayers, right, and Bernardine Dohrn.

Organizers passed out signs as a guitarist led a sing-along in Spanish, standing on a flatbed truck adorned with a banner that read: "Legalize Hard Working Immigrants."

Jim Rhodes, 71, of Logan Square was holding one end of a yellow banner that read "Health Care is a Human Right". A retired purchasing manager for an aluminum company and a grandfather of six, Rhodes said he belongs to a group that advocates for an expansion of Medicare to be the single-payer health provider for the whole country.

"I'm doing this for my kids and my grandkids," he said. "We want everyone to get a Medicare card when they're born and to give it up when they die."

Rhodes said the group brought 40 to 50 members today and they also plan to demonstrate on the NATO weekend at both the May 18 march organized by the California Nurses Association and the anti-war march on May 20.

As rain fell around 1:30 p.m., hundreds of May Day demonstrators left Union Park and headed downtown toward Federal Plaza.

McCarthy watched from a vantage point under a tree on the parkway at Washington and Ogden. As the march progressed, numerous police officers walked along the edges of the demonstration, maintaining a visible but low-profile presence in their normal blue-shirt duty uniforms.

As the march progressed, numerous police officers walked along the edges of the demonstration, maintaining a visible but low-profile presence in their normal blue-shirt duty uniforms.

Three to four bicycle officers stretched across each side street intersection to ensure the march did not splinter. And at times as marchers spilled on to the sidewalks police directed them back onto the street.

Early in the march someone lit firecrackers in the crowd. Some officers peered into the crowd but police did not seem concerned.

Closer to federal plaza, several trailers of police horses and their officer riders were standing by for crowd control.

As the march passed a Chase bank branch along Washington Street, protesters started chanting obscenities about JPMorgan Chase & Co. CEO Jamie Dimon.

As the march crossed a ramp leading to Interstate 90-94, police tried but failed to halt marchers for traffic backed up on the off ramp. A few trucks on the highway honked as the march went by.

Some in the crowd are trying out an obscene chant, "Chicago to Greece, (blank) the police."

As the crowd chanted, some demonstrators turned to Tobias and said "it's not personal" and "it's systemic, it's not you".

Tobias shrugged and bantered a bit with the marchers, asking one of them what would happen if there were no police. One of the marchers who apologized replied, "it would be really bad."

As demonstrators closed in on Federal Plaza, police on horseback joined the front of the march. Adams and then Dearborn streets were closed as police worked to funnel the marchers toward the plaza.

While some demonstrators shouted "free the horses," one police supervisor walking backward at the head of the march was tapped on the shoulder by a demonstrator who pointed out he was about to step in a large pile left by one of the horses. The officer thanked the man.

The Dirksen U. S. Courthouse remained open with people coming and going.

Dozens of protesters were already gathered in the area ahead of the march, some chanted "Hey hey, ho-ho, Rahm Emanuel's got to go."

Dori Ewing said she was there to protest the mayor's treatment of unions, primarily the teachers' union. She's not a teacher but has friends in a number of unions.

"If they mess with the teachers' union what's going to stop them from messing with the rest of them. Without unions there would be no middle class," Ewing said.

After a series of pro-labor speeches, the crowd at Federal Plaza began to disperse before the afternoon rush hour hit full swing. "See you next year," one of the last speakers said as the remnants of the crowd scattered in different directions.